Elliptical arch tool



Dec. 9, 1958 J. E. WEAVER 2,863,213

ELLIPTICAL ARCH TOOL Filed oct. so, 195sy INVENToR.

F76. G Ja//A/ 5. WEA Vie United States Patent ice 2,863,218 Patented Dec. `9,

ELLIPTICAL ARCH TOOL John E. Weaver`,`B'oulder, Colo. Applicationctober 30, 1956, Serial No. 619,219 1 Claim. (Cl. 33-31) This invention relates `to `scribing tools, and more particularly to an instrument for scribing elliptical arches for use in construction andin other activities.

A main object of the Vinvention is to provide a novel and improved instrument for drawing elliptical arches, said instrument being simple in construction, being easy to use, and being adjustable in accordance withthe 'size of the desired arch.

A further object'of the invention is to provide an improved scribing instrument for use in drawing elliptical arches in construction, sheet metal work, or other activities, the instrument being inexpensive to manufacture, being durable in construction, being compact in size, and involving only a fewl parts.

Further objects and advantages of the invention will become apparent from the following description and claim, and from `the accompanying drawings, wherein:

Figure 1 is a top plan- View sho-wing an improved scribing instrument according to the present invention set up for use in drawing an elliptical arch.

Figure 2 is an enlarged cross sectional View taken on the line 2 2 of Figure 1.

Figure 3 is an enlarged cross sectional View taken on the line 3-3 lof Figure l.

Figure 4 is an enlarged cross sectional view taken on theline 4-4 of Figure l.

`Figure 5 is a fragmentary top `planV detail view taken on the line 5 5 of Figure 4.

Figure 6 is an enlarged cross sectional view taken on the line 6-6 of Figure 1 and illustrating in dotted view a scribing pencil engaged in the aperture at the end of the scribing bar for marking the desired arch.

Referring to the drawings, 11 generally designates a scribing instrument according to this invention, the instrument comprising an el-ongated main bar 12 integrally formed with a transverse head 13 at one end thereof, the head 13 being formed at its edge with a guide groove 14, as shown in Figure 2, and being undercut at 15 to define the forwardly extending lip or ange 16. As is apparent from Figure 1, the head 13 extends equal distances on opposite sides of the elongated main bar 12, whereby to dene a substantially T-shaped body.

The main bar 12 is formed with a longitudinal guide groove 17 which is coextensive in length with said main bar, said groove 17 thus joining the groove 14 at the midpoint of said groove 14. The groove 17 is of inverted T-shape, and the bottom surfaces 18 of the opposite top flanges 19, 19 delined by said groove are located a substantial distance below the bottom surface 15 of the i'lange 16, as shown in Figure 2.

Designated at 20 is a scribing bar which comprises a pair of rod elements 21, 21 connected at their ends by respective transverse plate members 22 and 23, as shown in Figure 1, thus dening a unitary bar having a longitudinal central slot 24. Preferably, two plates 22 are employed at one end of the scribing bar 2li, one plate 22 being located on the top surfaces and the other plate 22 being located on the bottom surfaces of the end portions of rods 21, 21, the plates being secured to` vthe rods by rivets 25. Similarly, a pair of plates 23, 23 areipreferably employed at the opposite end of the scribing b'ar 20, the plate 23 being located on the top surfaces ofthe rod members 21, 21 and the plate member 23 1being located on the `bottom surfaces of 'said rod members, being secured to the rod members by rivets 26, asshown in Figure 6. The tp plate 23 is formedwith a central aperture `27 andthe bottom plate 23 is forni'ed'witha central aperture 27 Vsubstantially smaller than the `aperture 27 `butcoaxial therewith,iso that the point of a pencil, shown in dotted View at 28 may be engagedfthrough the apertures 27 and"27", allowing the pencil to markthesurface to be-scribedtina manner presently 'to be explained.

As shown in Figure `3v., a shouldered stud` 29is engaged through the tslot 24, saidfstud having ahead 30 which `is slidably received in the bottom of the T-shaped :groove `17, the shank 31fthe 'stud '29 being `slidably engaged inthe groove 24. AWingnut 32 is thradedly engaged on the `reduced top portion n33 of stud 29, the stud being provided with the cylindrical shoulder 34 between shank 31 and thefh'ead 31B which at times cooperates with "a washer `35 engaged on reduced shank portion 33 to clamp the `studto the barf20 when the wing nut 32 is tightened.

The stud`29 is clamped to the scribing `bar 20 at a position corresponding to one-half the overwall length'of the arch to be scribed. `This position is determine'dby placing the apertured end plates 23, 23 of the scribing bar v20 over a terminal point, for example the point 36 in Figure l ofthe arch to be scribed withthe scribing bar 20 `perpendicular to the groove 17, namely, wi'thtlie stud 29 at the top end ofthe groove, as viewed in Figure l. With `the Astud 29`in this position in the :groove 24, n"the wing nut 32 is tightened toclamp 1the stud'to the scribing bar 20.

Designated at 37 is a second shuldered "stud having a shankfportion 38 `engaged through A"the slot 24 of the scribing bar 20, thestud 37 being provided with ath'ead 39 which-is slidably engaged in thelower portion of the groove 14. The head39is of adiaineter suchthatfsaid head i's substantially lu'sh with the outer edge 4ll`of the head 13 of the instrument when j the intermediat'eshank portion `of the stud, shown at 41, engages against the edge lof ange 16. A wing nut 43 is provided on the stud 37, said wing nut being engageable against a clamping Washer 44 which cooperates with the intermediate shank portion 41 to clamp the stud 37 to the scribing bar 2i) at a selected position thereon when the wing nut 43 is tightened. The stud 37 is secured on the clamping bar at a position in accordance with the desired height of the arch to be scribed. Thus, in adjusting the position ot' the stud 37, the scribing bar Ztl is arranged in alignment with the stern portion 12 of the instrument with the slot 24 overlying the groove 17. The scribing bar 2d is then moved to a position such that the apertures in the plates 23 and 23 overlie the highest point of the proposed arch to be scribed, shown at 47 in Figure 1, the stud 37 being then located at the midpoint of the groove 14. The wing nut 43 is then tightened, locking the stud 37 in this position.

One of the bars 21 may be provided with a length scale 48, whereby the studs 29 and 37 may be locked in their desired positions on the scribing bar 20 in accordance with the actual specified distances of the points 36 and 47 from the center point Sit of the half-ellipse to be scribed, the distance between Vthe points 36 and Sil being equal to one-half the major diameter of the ellipse and the distance between the point Stb and the point 47 being onehalf the minor diameter of the ellipse.

Secured to the bottom surface of main bar 12 ilush with the edge 4i) `of the head 13 is an L-shaped bracket 52 having the rst arm 53 secured to bar .12 in any suitable manner, as by rivets 54 in longitudinal alignment therewith, and having the depending leg 55 extending perpendicular to the arm 53 and having its outer surface flush with the edge 40. The leg 55 is slidably engageable in a sleeve-like bracket 56 secured to the edge 57 of a table 58, or other horizontal work-supporting surface adapted to receive the board 59 or other member on which the arch is to be scribed. Thus, in a typical application of the instrument, the board 59 is placed on the table 58 and the instrument is connected to the table with the leg 55 slidably received in the sleeve-like bracket 56. The'studs 29 and 37 are set in their required positions in the groove 24, as above described, and the scribing bar 20 is placed so that it engages the top surface of the board 59, with the apertured plate members 23 and 23' overlying the starting point 36 of the arch to be scribed. A pencil 28, or similar scribing implement is engaged through the apertures 27 and 27', and the scribing bar 20 is then rotated, with stud 37 engaged with groove 14 and with stud 29 engaged in groove 17, the scribing bar 20 being rotated, for example, in a clockwise direction, whereby the scribing implement 28 is constrained to follow the path shown in full line view at 61) in Figure 1, namely, 'an elliptical arch, as required. As viewed in Figure 1, the scribing bar 20 reaches a vertical position, namely, a position in alignment with the stem portion 12 of the instrument when the scribing tool 28 reaches the highest point 47 of the arch. Thereafter, the scribing bar 20 rotates to a horizontal position in alignment with the head 13 of the implement when the pencil 28 reaches the terminal point, shown at 61, of the scribed arch.

A set screw 64 is provided in the sleeve-like bracket 56 so that leg 55 may be at times rigidly clamped to the bracket by tightening the set screw. Thus the tool may be held at any desired height relative to the table 58, and allowance can be thus made for the variation in thickness of the material that is to be scribed.

As shown in Figure 5, a washer 62 may be provided on each of the studs 29 and 37 engaging the top surface f the scribing bar 20, the washer being formed with oppositely directed pointer elements 63, 63, facilitating the placement of the stud elements along the numerical scale 48 when setting up the instrument for use.

While a specific embodiment of an improved instrument for scribing elliptical arches has been disclosed in the foregoing description, it will be understood that various modifications within the spirit of the invention may Occur to those skilled in the art. Therefore, it is intended that no limitations be placed on the invention except as defined by the scope of the appended claim.

What is claimed is:

In combination, a table having a straight edge, a vertical sleeve-like bracket member secured to said straight edge, an elongated main bar, a transverse head rigidly secured to one end of said main bar, said head being formed at its edge with a iirst guide groove, said main bar being formed with a second guide' groove extending longitudinally thereof, said second guide groove being substantially coextensive in length with said main bar and terminating at and communicating with said first guide groove, a scribing bar formed with a longitudinal slot and overlying said main bar and head, a first stud element adjustably secured to said scribing bar in said slot and being slidably engageable in said first guide groove, a second stud element adjustably secured to said scribing bar in said slot and being slidably engageable in said second guide groove, said scribing bar being formed with an aperture at its end to receive a scribing implement and to supportsaid implement for movement with said scribing bar, and a depending leg secured to the bottom surface of said main bar and extending perpendicular thereto, the outer surface of said leg being ush with the edge of said head, said depending leg being slidably received in said sleeve-like bracket member, whereby the edge of said head is supported for Vertical adjustment and for engagement with the edge of a workpiece supported on the table adjacent the table edge.

References Cited in the le of this patent mel, Popular Mechanics magazine, February 1944, page 135. 

